In the plumbing field, it is common to provide sewer lines, soil lines and drain lines with an access joint which will permit the removal of sewer or drain obstructions. Such access joints typically are sealed by means of a removable, threaded plug which is screwed into the access. Access plugs often rust or otherwise seize to the joint threads thereby preventing their removal and causing difficulty when a sewer blockage is to be removed. Several clean-out attachments are known which are said to make access and cleaning operations easier than would be provided by a clean-out plug and access joint; see, for example, U.S. Pat. Nos. 3,936,892, 3,805,826 and 3,927,860. These attachments and access fittings, however, do not prevent sewer back-up flow when a sewer line fitted with them is being cleaned. Moreover, sink traps fitted with such attachments tend to leak and cause soiling of the surrounding area.
It is, therefore, an object of the invention to develop an access fitting which will prevent uncontrolled discharge of backed-up sewerage and waste. A further object is the development of an access fitting which will permit sewer line cleaning without necessitating the removal of backed-up liquids in the line.